Flame retardant textile covered wire

ABSTRACT

A textile served wire coated with a flame retardant lacquer comprised essentially of a mixture, by weight, of 100 parts cellulose acetate base, 35 parts tricresyl phosphate plasticizer, 42.5 parts tris (2, 3 - dibromopropyl) phosphate flame retardant, and 128.5 parts acetone solvent.

United States Patent Boland et a1.

1541 FLAME RETARDANT TEXTILE COVERED WIRE UNITED STATES PATENTS Lommelet a1. ..106/177 UX 1 1 June 6, 1972 1,981,132 11/1934 Walsh et a1.106/177 2,126,850 8/1938 Whitehead 106/177 2,178,365 10/1939 Brobst106/177 2,574,515 11/1951 Walter et 211.. ..106/177 X 2,618,568 11/1952Meyer et a1... ...,.106/177 2,675,327 4/1954 Gearhart 106/176 3,412,0521 H1968 Taylor et a1 v.106/15 X 3,515,565 6/1970 Wood et a1. ..106/177Primary Examiner-Lorenzo B. Hayes Attorney-H. J. Winegar, R. P. Millerand A. J. Nugent [57] ABSTRACT A textile served wire coated with a flameretardant lacquer comprised essentially of a mixture, by weight, of 100parts cellulose acetate base, 35 parts tricresyl phosphate plasticizer,42.5 parts tris (2, 3 dibromopropyl) phosphate flame retardant, and128.5 parts acetone solvent.

4 Claims, 1 Drawing Figure PATENTEDJUR s 1972 INVENTORS Danlel E. BolundLeonard S. Dewees LeRoy M. Towsley ATTORNEYS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates toimprovements in flame retardant compositions, and more particularly, toa new and improved flame retardant lacquer for coating textile coveredwire, and to new and improved textile covered wire having its coveringcoated with such flame retardant lacquer.

In the production of textile served wire, which is particularly adaptedfor use in the so-called U-type distributing frames employed intelephone exchanges, it is common practice to extrude a flexiblepolyvinyl chloride insulating layer over the conductor wire. Wherefeasible, this insulating layer incorporates a suitable flame retardantplasticizer. This operation is followed by wrapping of the cottontextile serving over the insulation, whereupon the served wire is passedthrough an impregnating 'chamber wherein a substantially transparentlacquer coating is applied under pressure to prevent unraveling orfraying of the serving, while permitting visibility of the underlyingserving for identification purposes, the thickness of the coating beingcontrolled by passage of the wire out of the chamber through a rubberdie having a central aperture'of a predetermined size. The emergingcoated wire is continuously wound and air dried on a series of capstansprior to being reeled.

2. Description of the Prior Art A typical prior art lacquer. formulationemployed in the above process is as follows:

Ingredients Parts by Weight Cellulose Acetate I Tricresyl Phosphate 20Triphenyl Phosphate 35 Dimethyl Phthalate 30 Dibutyl Phthalate 8.75

' Acetone 148 (approx.)

While this lacquer possesses the physical characteristics necessary foruse in the wire coating process and is effective in serving the desiredpurposes of visibility of the serving and of preventing unraveling andfraying of such serving, it nevertheless is not sufficiently flameretardant. This is true particularly because of the presence of thephthalate plasticizers, which are flammable and tend to negate the flameretardant characteristics of the phosphate plasticizers.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of thepresent invention to provide a new and improved flame retardant lacquerwhich is just as feasible for use in the aforesaid wire coating processand just as effective in permitting visibility of the serving and inpreventing unraveling and fraying of such serving, as the aforesaidlacquer. To this end, the present lacquer is comprised essentially of amixture of a base, a plasticizer, a flame retardant and a solventpresent in the following proportions by weight: 100 parts of derivativeof cellulose (preferably celluloseacetate) as the base, between about 25and 35 parts of derivative or cresylic acid and phosphorous oxychloride(preferably 35 parts tricresyl phosphate) as the plasticizer, betweenabout 40 and 45 parts of a brominated monomeric triallyl phosphate(preferably 42.5 parts of tris (2,3 dibromopropyl) phosphate as theflame retardant, and between about 120 and 150 parts of dimethyl ketone,ethyl methyl ketone, ethanol or methanol (preferably 128.5 parts ofdimethyl ketone; i.e., acetone) as the solvent.

Another primary object is to provide a new and improved textile coveredwire having its covering coated with the aforesaid flame retardantlacquer.

Additional objects and advantages of the invention will become apparentupon consideration of the following detailed description andaccompanying drawing, wherein:

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is an enlarged sideelevational view of a textile served wire coated with the inventiveflame retardant lacquer and constitutes a preferred embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawing, the textile served wire is generally indicated at 10, andincludes a central conductor 12 surrounded by an insulating layer 14preferably formed of fire retardant plasticized polyvinyl chloride, apreferably cotton and color coded textile serving 16 wrapped aroundinsulating layer 14 which in turn is impregnated with and surrounded bythe inventive flame retardant lacquer coating 18. The coating issubstantially transparent for visibility of the underlying serv- Wire 10is particularly adapted for use in the so-called U- type distributingframes in telephone exchanges, and for this purpose its various elementshave the following typical physical characteristics. Conductor 12 ismade of 22AWG gauge copper wire, insulating layer 14 has an average wallthickness of 8 mils, serving 16 is made of 20/1 cotton yarn, and theweight of lacquer coating 18 ranges between about 60 and 80 milligramsper foot of wire, with the preferred weight being about 70 milligrams.

In producing wire 10, insulating layer 14 is extruded over conductor 12and serving 16 is wrapped around layer 14, such serving preferably beingprovided with a differently colored tracer thread (not shown) foridentification purposes. The textile served wire is then unreeled andpassed through an impregnating chamber (not shown) into which thelacquer is injected under pressure to form coating 18, the thickness andweight of which is controlled by passage of the coated wire out througha rubber sizing die (not shown) of the desired diame ter. As the coatedwire leaves the chamber it is wound continuously over a series of movingcapstans (not shown) to air dry lacquer coating 18 and is rereeled.

In order to successfully process wire 10, it is imperative that lacquercoating 18 have the following physical properties. First, it must besufliciently lubricious to pennit smooth passage through the sizing die.Secondly, it must be suffrciently fast drying to permit winding on thecapstans and reels without adhesion of the wire coating thereto or toitself. Third, it must have sufficient film flexibility to prevent thelacquer from cracking on the wire, particularly when wound on the reels.

While the prior art coating referred to above does possess thesephysical characteristics, it is not sufiiciently flame retardant.Accordingly, the principal problem to overcome was to eliminate theflammable phthalate plasticizers in order to obtain the desired flameretardance, while still maintaining the other physical characteristicsnecessary for successful coating of the wire. After extensiveexperimentation, which also involved replacement of the tire retardantphenyl phosphate fire retardant plasticizer with more tricresylphosphate because of its greater lubricity, the following formulationwas developed Comparative flame retardance tests were made between wireswhich had the physical characteristics described above for wire 10, andwere otherwise identical, except for the lacquer coating. In one test,wire 10, with the inventive 3 4 lacquer coating of the example, wasplaced on several shelves ethyl methyl ketone, ethanol or methanol maybe substituted, on a small distributing frame and a 4-inch diameter dishof aldimethyl ketone (i.e.; acetone) is preferred because it is thecohol was placed below a shelf and ignited. The wire most volatile forminimizing drying time and least toxic for withstood 12 minutes exposureto the alcohol flames with only minimizing exposure of personnel totoxic fumes. Slight burning and was self-extinguished immediately afterthe 5 Within the aforesaid ranges, the percentage of each inalcohol wasconsumed. In contrast, wire having the aforesaid gredient is criticalfrom the standpoint of both proper operaprior art lacquer coatingignited after about 1 minute in the altion of the coating process andobtaining the maximum practiecho! and the tire slowly spread bothhorizontally and vertical flame retardance. If too much flame retardantis used; i.e., cally. more than about 45 percent of the base, theformulation will In another test using the distributing frame mentionedcause adhesion to the capstans and will not run. If the above and wire10 with lacquer 18, the horizontal side of the plasticizer exceeds about35, percent of the base, it will conframe was ignited and produced astrong fire extending over tribute to the adhesion problems. Should theratio of the flame several shelves. Wire 10 burned only in the flames inthe rere rd nt o h pl i iz r exceed about /2 film gion of the terminalsand the fire did not propogate along the flexibility is adverselyaffected, while a ratio below about 8/7 wire. In a similar test usingwire with the prior an lacquer, the 1 0/35) un esi ably re uc s fl meretardance- This critical flames from the terminals spread along thewire and enlarged property is also adversely affected if the ratio ofthe combined the fire. percentage of the flame retardant and plasticizerto the base Accordingly, it is evident that wire coated with theinventive f l below about 1 Likewise, the ratio f he lacquer exhibitsgreatly improved flame retardance ove that total of the otheringredients to the solvent should not exceed coated with the prior artlacquer. At the same time, the invenabout nor Should it be 1888 thanabout l tive lacquer oating 18 al o o e e the h i l ha (165/ 150), inorder to control the viscosity for obtaining a teristics of lubricity,fast drying and film flexibility necessary p pe amount of lacquercoating on the wire, the optimum for efficient and effective processingof the wire during and amount being obtained h he pr rr r io f thexamafter coating, drying and rereeling. The coated wire 10 also 1 aboutv has been found to possess better handling characteristics than M themvfmuve lacquer descnbe? harem ls espec'ally the same wire coated withthe prim. an lacquer, the improve; suitable for coating the textilecovered wire referred to herein,

ment being attributed to a smoother outer surface. 5 also may be F tocoat other objects or y be formed Although the formulation of theexample represents a into filaments, ribbons, sheets, or otherconvenient forms by preferred embodiment of the inventive lacquer, thisformulaany f m know" m the tion can be varied within certain limits andstill produce an acwhat 15 claimed is: ceptable flame retardant lacquercoating. For example, while A f covered havmg covermg coated I acellulose acetate is preferred because of its electricalinsulatsubstajnuany transParerft flame retardant l Conslstmg ingproperties, other suitable derivatives of cellulose such as essenua'uyof a dned mlxmre of base a Pi f a flalne cellulose formate among theesters and ethyl cellulose among retardarft and a Solvent present Pnorto m the followmg the ethers y be used as the base proportions byweight: 100 parts of a derivat ve of cellulose as The preferredderivative of cresylic acid and phosphorous the base F Y about 25 and 35parts of mciesyl pho sphate oxychloride for use as the plasticizer istricresyl phosphate, the Plasnclzert between about and Parts of ms(2,3'because it not only provides the needed die lubrication and dlbmmopropylphosphate asthe flame retardant and between film flexibility but alsocontributes to flame retardance. Howabout 120 and 150 parts of dimethylketone' ethyl methyl ever, the amount of this ingredient may varybetween about 25 40 ketone' ethanol or [methanol as the and 35 parts per100 parts of base 2. The wire of claim 1 wherein said base 18 celluloseacetate. AS for the flame retardant a partially brominated 3. The wireof claim 2 wherein said solvent is dimethyl ketone.

monomeric triallyl phosphate is usable, but the fully brominatedphosphate of the example is preferred because of its greater flameretardance. This ingredient also functions as a secondary plasticizerand may vary in amount between 4. The wire of claim 3 wherein said base,plasticizer, flame 45 retardant and solvent are present prior to dryingin the following proportions: 100 parts cellulose acetate, 35 partstricresyl about 40 and 45 parts per 100 pans of base phosphate, 42.5tris (2, 3 dibromopropyl) phosphate,

While the quantity of solvent may range between about 120 and 128's pansdlmethyl ketone' and 150 parts per 100 parts of base, and other solventssuch as STATESAT was I 3,668 ,302 Data June a 1972 Patent inventor)Daniel E. Boland-Leonard S. DeWees-Leroy M. Towsley It iscertifiedmaterror appears in the above-identified patent and that saidLetters Patent are hereby corrected as shown below:

In the specification, Column l, line 35 Claim 1 insert following theword "cellulose", -selected from the group consisting of celluloseesters and cellulose ethers--.'

Signed and sealed this 14th day of January 1975.

(SEAL) Aittests McCOY M. GIBSON' JR; 0; MARSHALL DANN Cissioner ofPatents Attesting Officer L-566-PT 3,668 ,302 Datea June 6, 1972 PatentNo.

inventor) Daniel E. Boland-Leonard S. DeWees-Leroy M. Towsley It iscertified- (hazelnut appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

I In the specification, Column line 35 Claim 1 insert following the word"cellulose", ---selected. from the group consi stinjg of celluloseesters and cellulose ethers-.

Signed and sealed this 14th day of January 1975.'

(SEAL) Attests' McCOY M. GiBSON' JR. Attesting Officer 0; MARSHALL 1mmCommissioner of Patents

2. The wire of claim 1 wherein said base is cellulose acetate.
 3. The wire of claim 2 wherein said solvent is dimethyl ketone.
 4. The wire of claim 3 wherein said base, plasticizer, flame retardant and solvent are present prior to drying in the following proportions: 100 parts cellulose acetate, 35 parts tricresyl phosphate, 42.5 parts tris (2, 3 - dibromopropyl) phosphate, and 128.5 parts dimethyl ketone. 